1. Field of the Invention
The present invention relates generally to ultrasonic inspection devices, and more particularly to an apparatus which detects the presence of fatigue cracks in structure surrounding a rivet or other type of a fastener, as in aircraft structure, for example.
Aircraft maintenance requires constant inspections for cracks resulting from stresses imposed during flight. Failure to detect such cracks in a critical aircraft part or structure can ultimately result in catastrophic failure of the part and, as well known, loss of the aircraft and the lives of the passengers.
2. Description of the Prior Art
Nondestructive testing apparatus using ultrasonic test probe assemblies have been used for inspecting weld beads, bonding adhesives, journals of railroad cars and for sensing the depth of cellular pits or cells in a surface. The present invention is a hand-held device incorporating several unique features, not taught in the prior art, which permits the detection of cracks in a structure around a fastener even when the cracks in the structure are plated or painted over.